import java.util.*;

public class FIFOQueue
{
	 private LinkedList A;
	 public FIFOQueue() { A = new LinkedList();}
	 public void enqueue(Object o){ A.add(o); }
	 public Object dequeue() { Object tmp = A.removeFirst(); return tmp;}
	 public int size() { return A.size();}
	 public boolean isEmpty() { return (A.size()==0);}
}